In some aspects, self-balancing vehicles are controlled through a yaw or steering control structure. For example, turning of the self-balancing vehicles may be achieved through a handle bar structure that ascends from the platform upward toward the chest of a user. FIG. 1 illustrates one example of a conventional two-wheel self-balancing vehicle with a yaw or steering control structure. The conventional two-wheel self-balancing vehicle with a yaw or steering control structure utilizes a control principle of a single inverted pendulum system.
As shown in FIG. 1, a two-wheel self-balancing vehicle 100 with a yaw or steering control structure comprises a first wheel with direct current (DC) motor 10, a second wheel with DC motor 12, a foot placement section 14 and a yaw or steering control structure 16. With two parallel wheels controlled independently by two DC motors, two-wheel self-balancing vehicle 100 can move forward, backward, and make relatively stable turns. The maximum moving speed of two-wheel self-balancing vehicle 100 could be up to 10 miles per hour. To operate two-wheel self-balancing vehicle 100, a user may stand on foot placement section 14, and the user's feet are separated to left and right. Foot placement section 14 may be one section or area affixed to first wheel with DC motor 10 and second wheel with DC motor 12. Foot placement section 14 may comprise a first portion 11 and a second portion 13 located on the same plane. Yaw or steering control structure 16 may comprise a handle bar structure, including for example, a grip, a handle, and/or a pole.
By sloping forward or leaning backward the user's body, the user can control two-wheel self-balancing vehicle 100 to accelerate or decelerate. A left turn or a right turn may be accomplished by sending the turn signals through yaw or steering control structure 16. One of the disadvantages of this design is that with yaw or steering control structure 16, two-wheel self-balancing vehicle 100 is larger and heavier than a vehicle without a central control structure (e.g., a handle bar structure). The user also has to exert hand control using yaw or steering control 16.
FIG. 2 illustrates one example of a control diagram 200 of two-wheel self-balancing vehicle 100. As shown in FIG. 2, micro-electro-mechanical systems (MEMS) sensors, such as an accelerometer and a gyroscope may be used to detect the inclination angle of foot placement section 14. The inclination angle of foot placement section 14 may be used in combination with yaw or steering control input from yaw or steering control structure 16 as input signals to a proportional-integral-derivative (PID) control and driving control of two-wheel self-balancing vehicle 100.
FIG. 3 illustrates an embodiment showing the inclination angle of foot placement section 14 of two-wheel self-balancing vehicle 100. As shown in FIG. 3, when foot placement section 14 is tilted down or up by the user, the accelerometer and gyroscope sensor sense the motion and calculate the inclination angle. The inclination angle information, after being compared with a desired balance angle, may be sent to the PID and center control unit. Together with the yaw and steering control input, DC motor control signals may be generated and sent to a driver to control the movement of first wheel with DC motor 10 and second wheel with DC motor 12 to maintain the balance of two-wheel self-balancing vehicle 100. For signal processing purpose, the PID and center control unit may also receive the current speed information from first wheel with DC motor 10 and second wheel with DC motor 12, and the current information from drivers.
In this implementation, two-wheel self-balancing vehicle 100 may suffer from their large size and dimensions of the yaw or steering structure, which may be required to handle the vehicle's turn movement. This may result in the vehicle's incapability to turn surrounding its own center of gravity.
In some aspects, self-balancing vehicles have two platform sections or areas that areas that are independently movable with respect to one another and that thereby provide independent control and/or drive of the wheel associated with the given platform section/area. The angle control of self-balancing vehicles have two platform sections or areas can be achieved by measuring the angle difference between the left and right sides' angle difference, thus eliminating the need for a structure for controlling.
FIG. 4 illustrates an example of a two-wheel self-balancing vehicle 400 having independently movable foot placement sections. In this embodiment, a first foot placement section 42 and a second foot placement section 44 can move independently from each other, which may eliminate the need of a yaw and steeling control structure, and make space for the center space between the left side of second foot placement section 44 and the right side of first foot placement section 42. A first sensor and control module, which includes an accelerometer and a first gyroscope, may be required on first foot placement section 42 sense the tilted angle of first foot placement section 42. A second sensor and control module, which includes an accelerometer and a first gyroscope, may be required on second foot placement section 44 to sense the tilted angle of second foot placement section 44.
FIG. 5 illustrates an embodiment of a control diagram of a two-wheel self-balancing vehicle having independently movable foot placement sections. As illustrated in FIG. 5, the yaw angle information may be extracted from the tilted angle information obtained from the first sensor and control module and second sensor and control module, as described with reference to FIG. 4. FIG. 6 illustrates an embodiment showing an example of turning movement examples of a two-wheel self-balancing vehicle having independently movable foot placement sections. FIG. 6 illustrates one or more turn movement examples by operating first foot placement section 42 and second foot placement section 44 separately.
However, since each of first foot placement section 42 and second foot placement section 44 moves independently around a center axis of the two-wheel self-balancing vehicle having independently movable foot placement sections, constrains may be introduced to the mechanical design as well as the exterior design of the vehicle. In addition, users operating two-wheel self-balancing vehicle 400 having independently movable foot placement sections would find it difficult to circle around a center point of gravity that is the user himself or herself. Additionally, because first foot placement section 42 and second foot placement section 44 are separated, the center portion between first foot placement section 42 and second foot placement section 44 cannot hold any additional functionalities or accessories. Furthermore, the design of the two-wheel self-balancing vehicle having independently movable foot placement sections also introduces additional costs due to, for example, first foot placement section 42 and second foot placement section 44 being separated.